arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0909.1102cs.LOcs.CC
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单计数器过程的分支时间模型检验

Branching-time model checking of one-counter processes

Stefan Göller, Markus Lohrey

摘要:

单计数器进程(OCP)是下推进程,只对一元堆栈字母表进行操作。研究了基于OCP的模型检验计算树逻辑(CTL)的计算复杂性。一个PSPACE上界是继承自该问题的模态μ演算。首先,我们分析了OCP上CTL的周期性行为,并推导出一种模型检验算法,其运行时间仅在控制位置数量方面呈指数级,以及我们称之为向左直到深度的公式的语法概念。因此,模型检验固定OCP对CTL公式与一个固定的深度,直到在P。这概括了第一作者,Mayr,和到CTL的片段EF的表达复杂性的结果。其次,我们证明了在一定的OCP上,CTL模型检验是PSPACE困难的。第三,我们表明,已经存在一个固定的CTL公式,模型检验的OCP是PSPACE困难的。为了得到后一个结果,我们使用了复杂性理论中的两个结果:(i)将中国余数表示中的自然数转换为二进制表示是在对数空间一致的NC ^1中;(ii)PSPACE是AC ^0-可串行化的。我们证明,我们的方法可以用来获得进一步的结果。我们证明了在OCP上对CTL的片段EF进行模型检验对于P^NP是困难的,从而建立了一个匹配的下界,并回答了第一作者Mayr和To的一个公开问题。我们还证明了以下问题对于PSPACE是困难的:给定一个计数器马尔可夫决策过程,一组计数器值为零的目标状态和一个初始状态,以决定初始状态最终到达目标状态之一的概率是否任意接近1。这提高了以前已知的下界的每一个层次的布尔Brazdil等人。

英文摘要:

One-counter processes (OCPs) are pushdown processes which operate only on a unary stack alphabet. We study the computational complexity of model checking computation tree logic (CTL) over OCPs. A PSPACE upper bound is inherited from the modal mu-calculus for this problem. First, we analyze the periodic behaviour of CTL over OCPs and derive a model checking algorithm whose running time is exponential only in the number of control locations and a syntactic notion of the formula that we call leftward until depth. Thus, model checking fixed OCPs against CTL formulas with a fixed leftward until depth is in P. This generalizes a result of the first author, Mayr, and To for the expression complexity of CTL's fragment EF. Second, we prove that already over some fixed OCP, CTL model checking is PSPACE-hard. Third, we show that there already exists a fixed CTL formula for which model checking of OCPs is PSPACE-hard. To obtain the latter result, we employ two results from complexity theory: (i) Converting a natural number in Chinese remainder presentation into binary presentation is in logspace-uniform NC^1 and (ii) PSPACE is AC^0-serializable. We demonstrate that our approach can be used to obtain further results. We show that model-checking CTL's fragment EF over OCPs is hard for P^NP, thus establishing a matching lower bound and answering an open question of the first author, Mayr, and To. We moreover show that the following problem is hard for PSPACE: Given a one-counter Markov decision process, a set of target states with counter value zero each, and an initial state, to decide whether the probability that the initial state will eventually reach one of the target states is arbitrarily close to 1. This improves a previously known lower bound for every level of the Boolean hierarchy by Brazdil et al.

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